<style>
.topnav a {
  display: none;
  border: 1px solid #dfdfdf;
  background: #f5f5f5;
  width: 43px;
  height: 43px;
  text-align: center;
  overflow: hidden;
}
.topnav a i.btn-top {
  display: block;
  width: 30px;
  height: 30px;
  background: url(../images/icons.png) no-repeat;
  background-position: 0 -321px;
  margin: 0 auto;
  margin-top: 12px;
  transition: all 0.2s;
}

.topnav a:hover {
  background: #7f4ee5;
  color: #fff;
}

.topnav a:hover i.btn-top {
  margin-top: 8px;
  background: url(../images/icons.png) no-repeat;
  background-position: 0 -355px;
  width: 30px;
}

</style>

    <a href="javascript:;"><i class="comicon btn-top"></i></a>









